I think it is just you. Like many similar incidents, the news report are never clear. Also another news report suggests that the group did have bear spray.

A few things to keep in mind though.

Making noise while hiking whether it be loud talking, singing etc is standard for bear country. Is if effective 100% of the time? Obviously not, however making noise in bear country is recommended by many experts who have extensive bear behavioral knowledge.

The group was attacked at a river crossing. This time of year, the water is flowing fast, loud and is almost impossible to hear anything around you and the same goes for the bear. Yes you can argue that the group should of been more aware but we don't know the exact details as we were not there. Depending on the immediate terrain and vegetation, a bear or any animal can be 20 feet from you and not even be noticeable.

Also grizzly bears are well known for being territorial, especially around their coveted fishing spots on the river. The group was actually in the middle of crossing the river when the bear attacked, so yes the territorial aspect may of played part?

In regards to the school allowing these teenagers out on their own in the wilderness without an instructor. The same attack may of occurred with the instructor there also.

As in many of these incidents, there are too many "known unknowns" to attempt to armchair and not second guess or criticize what happened 1000's of miles away...